During aerial refueling operations, the rate of closure between a tanker aircraft and a receiver aircraft must be controlled to ensure that excessive rates of closure do not jeopardize the safety of the aircraft and their crews. For at least this reason, it sometimes becomes necessary for a boom operator and/or a pilot to cancel a refueling sortie when the rate of closure becomes excessive.
An inexperienced receiver aircraft pilot, for example during aerial refueling training, may have difficulty in subjectively determining the appropriate airspeed at which to approach the tanker aircraft to maintain an acceptable rate of, closure between the tanker and receiver aircraft. Accordingly, the training envelope during such sorties can be expanded by providing rate of closure information to both the boom operator and the receiver aircraft pilot.